Researchers evolve a multicellular yeast in the lab in 2 months

The rise of multicellular plants, animals, and fungi allowed vast increases in …

When we think of life on Earth, most of us think of multicellular organisms, like large mammals or massive trees. But we're only aware of three groups of complex, multicellular organisms, which suggested it might be a major hurdle. Now, a new study describes how researchers evolved a multicellular form of yeast (the same species that contributes to bread and beer), and were able to see specialized cell behaviors and reproduction in as little as 60 days.

The authors lay out the problem very simply in their introduction, stating that, "Multicellularity was one of the most significant innovations in the history of life, but its initial evolution remains poorly understood." There is some evidence that it can be a favorable trait—research shows that clusters of cells evolve when a single-celled organism is kept in culture with a predator that can only swallow one cell at a time.

But that's about as far as these experiments went. It wasn't clear how these clusters of cells formed, whether they were genetically related, or whether they engaged in any sort of specialized behavior. More significantly, it wasn't obvious whether these clusters took a sort of "every cell for itself" approach to reproduction. So, although this work showed a multicellular lifestyle could be selected for, the researchers didn't look into how far down the road towards specialization those cells would go.

The new study attempts to follow more the behavior of simple multicellular groups more closely. It uses baker's yeast (Saccharomyces cerevisiae), an organism that normally grows as single cells. The authors grew these in culture and, once a day, transferred them in a way that favored multicellular growth.

Their method was pretty simple. Normally, yeast are grown in a culture that's shaken, and the single cells will only slowly settle to the bottom when that's stopped. The authors only transferred the cells at the bottom of the culture to fresh food, so that they selected for those cells that settled to the bottom quickly. This favors large clusters of cells, instead of single ones.

With only 60 daily transfers, all of their experimental populations were dominated by yeast cells that grew as clusters, which the authors describe as "roughly spherical snowflake-like." These were formed because, instead of separating after they divided, cells would remain attached, expanding the cluster with each division. Although this comes at a cost compared to individual cells—the authors calculate that individual cells in the cluster are 10 percent less fit than their single-celled relatives when they're not selecting for things on the bottom. But, with the selection in place, the clusters had a huge advantage.

But the clusters didn't simply keep growing indefinitely. Instead, the yeast quickly evolved a form of reproduction by splitting off what the authors call "propagules," or smaller clusters that break off and go on to develop on their own.

With more generations, this form of reproduction began to include specialized cell behavior. A small percentage of cells in the cluster would start committing suicide through a process called apoptosis. This death would allow the propagule to split off cleanly at the site of the dead cell, improving the efficiency of reproduction. Normally, there's no evolutionary advantage to a cell ending up dead but, since the cells in the propagule are genetically identical, this behavior can be selected for.

This new form of growth and reproduction is still a long way off from the complex, specialized tissues found in most multicellular organisms. But the ease with which this behavior evolved suggests that the foundations of multicellularity may evolve very easily, and don't present the barrier to complexity that many people have assumed it was.

86 Reader Comments

We have never seen it, directly observed it nor caused it in a laboratory. This isn't poorly understood it's simply poor science. We have effectively cornered ourselves into only one possibility and have no other choice but to prove it's existence.

Most likely this multicellular behavior exploits processes that are involved in some form of social behavior in single celled yeast. Such behavior is likely to be common in single celled organisms. This kind of multicellular activity may not be too different than sponges. But evolution of the first Metazoan with a bilateral body plan involved much more. For example, a nervous system, muscle, and the root developmental program of all bilateral Metazoans. It is likely most of this evolution is also based on biochemical activities that were already present in single celled Eukaryotes. Actin, for example, seems to be a central structural protein in all animal cells as well as one of the two major proteins in muscle cells. But a large amount of evolution surely was needed to generate the prototype of all the more complex animals on Earth. It must of taken millions of years. But it may have been quick enough not to take hundreds of millions of years. It could be a reasonably rapid event on the time scale of the Earth's fossil record.

This whole article just makes me want to go buy a jar of yeast and play God for a while. The process used doesn't seem out of reach for the average Joe.

In reality, I'll probably just end up with a huge stinking mess. In some weird corner of my mind, though, I keep seeing a tiny civilization forming in the bathtub....

I've taken up home brewing and have a few sachets of dry yeast in my 'fridge. When I get home tonight, I'll see if I can get them to evolve as far as simple aquatic forms. Next week, maybe the one after, I'll try for land animals.

We have never seen it, directly observed it nor caused it in a laboratory. This isn't poorly understood it's simply poor science. We have effectively cornered ourselves into only one possibility and have no other choice but to prove it's existence.

No. The alternatives are of course on the table, if something suggests them. Or if we never do put together anymore evidence that this is how it happened.

So what is your proposal for an alternate path? Abiogenesis already in a multicellular form? A external non-biological agent that triggered the evolution more directly and drastically than simple selection?

The later is still really evolution, although getting into specifics, so it isn’t remotely off the table. It just isn’t the possible general path that this experiment tried out.

The former is an intriguing idea, although without any evidence to support it popping up, the similarity between multi cell organisms and single cell organisms, it is hardly “poor science” to consider it a lower likelihood of occurring. I suppose that could be addressed by single cell organisms evolving from multicellular forms. Counter-intuitive but that alone doesn’t rule it out.

This whole article just makes me want to go buy a jar of yeast and play God for a while. The process used doesn't seem out of reach for the average Joe.

In reality, I'll probably just end up with a huge stinking mess. In some weird corner of my mind, though, I keep seeing a tiny civilization forming in the bathtub....

I've taken up home brewing and have a few sachets of dry yeast in my 'fridge. When I get home tonight, I'll see if I can get them to evolve as far as simple aquatic forms. Next week, maybe the one after, I'll try for land animals.

If I'm lucky, I can get them to evolve as fast as things seem to in Spore. Starting from yeast, though, I keep picturing Jabba the Hut types(and reeking of booze at that!). Not that I'd be upset with that, but I'm hoping for something with at least rudimentary legs. Within a month or so, anyway. After that, they'd better figure out how to smelt metals from the rocks I strategically place on the soap-holder. Otherwise I'll be terribly disappointed and probably start fresh.

This whole article just makes me want to go buy a jar of yeast and play God for a while. The process used doesn't seem out of reach for the average Joe.

In reality, I'll probably just end up with a huge stinking mess. In some weird corner of my mind, though, I keep seeing a tiny civilization forming in the bathtub....

I've taken up home brewing and have a few sachets of dry yeast in my 'fridge. When I get home tonight, I'll see if I can get them to evolve as far as simple aquatic forms. Next week, maybe the one after, I'll try for land animals.

If I'm lucky, I can get them to evolve as fast as things seem to in Spore. Starting from yeast, though, I keep picturing Jabba the Hut types(and reeking of booze at that!). Not that I'd be upset with that, but I'm hoping for something with at least rudimentary legs. Within a month or so, anyway. After that, they'd better figure out how to smelt metals from the rocks I strategically place on the soap-holder. Otherwise I'll be terribly disappointed and probably start fresh.

Should be doable, once you manage to locate the controls for accelerating the time scale of RealLife.

It hurts some people's heads to read things they disagree with. I too think the evolution skeptics are bonkers, but I find them entertaining, and unless they are faking it, they aren't trolls.

To got more on topic - here's what he said:

"We have never seen it, directly observed it nor caused it in a laboratory. This isn't poorly understood it's simply poor science. We have effectively cornered ourselves into only one possibility and have no other choice but to prove it's existence."

We've observed the evolution of multicellular life in this experiment. It's alive. It lives in clumps which contains cells which are genetically identical, and which specialize to perform different functions. That sounds like multicellular life to me. Sure, it's pretty damned primitive, and I'd love to see such experiments continued for longer periods of times, but I suspect that even with very strong artificial selection we are still looking at hundreds if not thousands of years before you'd get something truly interesting.

Regardless, this small experiment presents a plausible rung on the ladder to the evolution of complex multicellular life. Do you have a better explanation?

It hurts some people's heads to read things they disagree with. I too think the evolution skeptics are bonkers, but I find them entertaining, and unless they are faking it, they aren't trolls.

The problem is that they derail the conversation from what could be an interesting discussion of the topic at hand into a stupid debate based on their religious or political values. Rather than gaining a better understanding of the science involved, we instead get a bunch of noise and the knowledgable stay away as it is pointless to participate.

Signal to noise ratio control is what a moderator provides. And I'd be perfectly happy if in the process of moderating this thread they removed the posts about moderating this thread, including mine.

How exactly did cells start to die off consistently in the right places? It sound like they "already knew" this might happen and "recognized" the circumstances (lacking better words). 60*30*2 doesn't sound like enough chances for something like this to happen randomly with a positive effect.

How exactly did cells start to die off consistently in the right places? It sound like they "already knew" this might happen and "recognized" the circumstances (lacking better words). 60*30*2 doesn't sound like enough chances for something like this to happen randomly with a positive effect.

It was more than 60*30*2 (the article says "With more generations, this form of reproduction began to include specialized cell behavior"). How many more, we don't know.

However, we do know this: however many it was, obviously was enough, because it did in fact happen. Lastly, it didn't happen 'randomly'; it was the result of selection pressure due to the advantage it conferred.

It hurts some people's heads to read things they disagree with. I too think the evolution skeptics are bonkers, but I find them entertaining, and unless they are faking it, they aren't trolls.

To got more on topic - here's what he said:

"We have never seen it, directly observed it nor caused it in a laboratory. This isn't poorly understood it's simply poor science. We have effectively cornered ourselves into only one possibility and have no other choice but to prove it's existence."

We've observed the evolution of multicellular life in this experiment. It's alive. It lives in clumps which contains cells which are genetically identical, and which specialize to perform different functions. That sounds like multicellular life to me. Sure, it's pretty damned primitive, and I'd love to see such experiments continued for longer periods of times, but I suspect that even with very strong artificial selection we are still looking at hundreds if not thousands of years before you'd get something truly interesting.

Regardless, this small experiment presents a plausible rung on the ladder to the evolution of complex multicellular life. Do you have a better explanation?

We are attempting to fill in the blanks of a pre determined course. We have assumed it happened this way so we do experiments to prove it happened this way. I remember in college taking my first genetics class and asking the professor to explain to me how in such a short time, singular cellular life evolved into the diversity we have now. I have argued and will continue to argue that billions of years would not be enough as evolution as defined is very random. The only way we could have evolved in this short period of time is if the path was completely linear with very little or no diversions (no one has been able to explain to me the very linear path humans evolved to from common simian ancestors and how the planet isn't littered with fossils from failed mutations. The second being how did humans evolve so far advanced from the rest of our animal brethren? It flies in the very face of this theory.)To me it's just poor science and is nothing more than what I like to call "Faith based Science". We don't know how, why or how long it took, and we cannot replicate it in experiments, and we have never observed it happening in the wild, but we know it happened the way we think.However, I found the experiment interesting nonetheless

have argued and will continue to argue that billions of years would not be enough as evolution as defined is very random.

Not really. Never underestimate the power of non-random selective pressures acting on random mutations in the background. Like the non-random pressure of yeasts that are clumpier surviving to reproduce. For all the millennia we've been culturing yeast, apparently all it took was a couple of months of continuous selective pressure towards multicellularity for it to take hold.

btw, do we want folks to just simply agree with whatever is written? What place can we go as humans there won't be a difference of opinion? I am fascinated by science, and I love to ready articles and immerse myself in certain fields, however I take these articles with a grain of salt as I don't agree with the premise of the science in the first place. Lack of dissension is what leads to poor science. If folks were not allowed to speak up and question what were once though to be concrete truths, then we would have never had the discoveries of today.

But alas, it is human nature to remove those who disagree. I wonder where that trait "evolved" from?

have argued and will continue to argue that billions of years would not be enough as evolution as defined is very random.

Not really. Never underestimate the power of non-random selective pressures acting on random mutations in the background. Like the non-random pressure of yeasts that are clumpier surviving to reproduce. For all the millennia we've been culturing yeast, apparently all it took was a couple of months of continuous selective pressure towards multicellularity for it to take hold.

and to mutate into a whale? A human? An Ape? To create biodiversity across the planet? remember this is order from randomness, not the opposite. How did such chaos produce such order?

and to mutate into a whale? A human? An Ape? To create biodiversity across the planet?

It's a big planet, and a billion years is a long time. That's a ton of parallel experiments, especially given how much life there is in a cubic foot of soil. I think you underestimate not only the power of non-random selection, but also just how much stuff there is out there to exploit for life, and how many ways to exploit it.

and to mutate into a whale? A human? An Ape? To create biodiversity across the planet?

It's a big planet, and a billion years is a long time. That's a ton of parallel experiments, especially given how much life there is in a cubic foot of soil. I think you underestimate not only the power of non-random selection, but also just how much stuff there is out there to exploit for life, and how many ways to exploit it.

Quote:

remember this is order from randomness...

No it isn't. I just got done explaining that, didn't I?

Again we go back to selection. These mechanisms weren't in place. There was no life, at all. There was no natural selection. Only basic raw materials and randomness. What they produced in a laboratory was ordered pressure on existing life. This earth has never been ordered, thus the reason for our extreme weather, volcanoes, ice ages, possible asteroid collisions, catastrophic die offs. How can something that was not alive before try to survive? Life is too complicated to have come from basic chemicals in just a couple billion years, especially in the midst of all these environment changing events we see evidence of.

We are attempting to fill in the blanks of a pre determined course. We have assumed it happened this way so we do experiments to prove it happened this way.

The truth of the matter is that we did NOT start here. We started in a very different place. This is where we have reached, based on observations, poking around, and putting the pieces together. Could this all be the wrong path entirely? *shrug* Sure, but the evidence so far suggests otherwise.

I take it you don’t actually have any other alternatives to put forward, given you’ve ignored my previous post?

theJonTech wrote:

I have argued and will continue to argue that billions of years would not be enough as evolution as defined is very random.

When you did this arguing what evidence and train of logic do you employ, beyond the empty handwaving in your posts here?

Quote:

btw, do we want folks to just simply agree with whatever is written? What place can we go as humans there won't be a difference of opinion?

If you had something to back up your assertions on difference of opinion other than "by gosh, billions of years is a short time" that’d help.

According to the Nature news article multicellular life has arisen at least 25 times. Also the article points out that yeast have multicellular ancestors so it is possible that they still have the ability to be multicellular, but as this occurred billions of generations ago its thought likely that the genes for this would have been lost (though I don't see why they couldn't have been co-opted for some other function).

Again we go back to selection. These mechanisms weren't in place. There was no life, at all. There was no natural selection. Only basic raw materials and randomness.

So what you're REALLY talking about is abiogenesis, which is different. And you're still wrong, it's not all randomness. Does oxygen bond to gold just as often as it bonds to carbon? No. Do platinum and argon bond together as frequently as chlorine and calcium? Hell no. Do you expect to find the same chemical products at the warm surface of a sea as near the frozen sea floor? Uh-uh. Are you going to find equal amounts of sulfurous chemicals in the volcano-less tundras of Siberia as you're going to find around the boiling hot springs of Yellowstone National Park? Survey says....nope! These are not random things. Even without life there is still selective pressure in the form of chemical affinities and thermodynamics, at the very least. It's not like shaking a bag of marbles and drawing one blind, it's like shaking a bag of mixed marbles and ball bearings and reaching into it with a magnet. Pretending that the chemistry of abiogenesis behaves randomly is the biggest mistake people can make.

This whole article just makes me want to go buy a jar of yeast and play God for a while. The process used doesn't seem out of reach for the average Joe.

In reality, I'll probably just end up with a huge stinking mess. In some weird corner of my mind, though, I keep seeing a tiny civilization forming in the bathtub....

I've taken up home brewing and have a few sachets of dry yeast in my 'fridge. When I get home tonight, I'll see if I can get them to evolve as far as simple aquatic forms. Next week, maybe the one after, I'll try for land animals.

If you fail, just remember Charlie Papazian's advice: "Relax-- have a homebrew!"

Most likely this multicellular behavior exploits processes that are involved in some form of social behavior

In this case, mother and daughter cells stay attached after a new daughter cell is reproduced. As more and more daughter cells are produced, a multicellular 'snowflake' develops. The cluster reproduces when one of the many-celled branches of a snowflake breaks off. One might think of this as a kind of behavioral alteration; in 'normal' yeast, the daughter cell separates from the mother cell.

have argued and will continue to argue that billions of years would not be enough as evolution as defined is very random.

Not really. Never underestimate the power of non-random selective pressures acting on random mutations in the background. Like the non-random pressure of yeasts that are clumpier surviving to reproduce. For all the millennia we've been culturing yeast, apparently all it took was a couple of months of continuous selective pressure towards multicellularity for it to take hold.

and to mutate into a whale? A human? An Ape? To create biodiversity across the planet? remember this is order from randomness, not the opposite. How did such chaos produce such order?

Except that you can do the math on mutation rates. Try reading "The Making of the Fittest" by Sean B. Carroll.

To me it's just poor science and is nothing more than what I like to call "Faith based Science". We don't know how, why or how long it took, and we cannot replicate it in experiments, and we have never observed it happening in the wild, but we know it happened the way we think.

I too am flabbergasted by the scale and complexity involved, but that is not a scientific critique. The problem with your argument (at least in how you have stated it so far), is that you have presented no evidence that life is too complex to have evolved. Rather, you "don't agree with the premise." That kind of gut instinct is exactly the feeling that has to be distrusted when it comes to doing science.

As Wheels said, really don't underestimate the power of running simultaneous experiments on every single living organism since life first developed. Also, we are surrounded by our mutant brethren: every other species on earth, every single fossil, and every human statistical outlier you meet. Most of the time mutations are small and add no selective pressure, or they die out, or they are folded back into some subset of a population (not every man can resist those neanderthal hips), but they're there, and sometimes they accumulate.

Also the article points out that yeast have multicellular ancestors so it is possible that they still have the ability to be multicellular, but as this occurred billions of generations ago its thought likely that the genes for this would have been lost (though I don't see why they couldn't have been co-opted for some other function).

Exactly. It reeked of a rigged experiment since they had to have already known this from the start. These yeast didn't "evolve" anything in the lab. The people running the experiment simply killed the ones that didn't clump together like they wanted.

The whole thing sounds to me like they did this in order to fool the masses into believing it. It's Eugenics, not evolution.

Also the article points out that yeast have multicellular ancestors so it is possible that they still have the ability to be multicellular, but as this occurred billions of generations ago its thought likely that the genes for this would have been lost (though I don't see why they couldn't have been co-opted for some other function).

Exactly. It reeked of a rigged experiment since they had to have already known this from the start. These yeast didn't "evolve" anything in the lab.

Even if this is the re-appearance of a variant strain of yeast that once again has the ability to form multicellular clumps and reproduce in a way we don't see other modern yeast doing that's still evolution. The yeast they ended up with was not simply a bunch of genetically different individuals stuck together but genetically identical ones; it's not as simple as sticky yeast. The idea that this is an old feature that's merely been dormant but reactivated is speculative, too. I'm pretty surprised that you're willing to disparage this study on such a flimsy basis.

@WoC: The selection might be non-random, but the appearance of these beneficial "features" aren't (or it might not even qualify as "evolution").

Well, the determination of what's beneficial or detrimental depends in large part on those non-random pressures. A normally-brown species of rabbit producing a mutant white-furred individual, for example. In the temperate or tropical areas, that's a detrimental trait: white fur is easier to spot against a background of dirt and plants. In a snowy environment, however, it's a boon: brown rabbits would stand out more and be more likely caught by predators. Hence the non-random selection acting on random genetic changes. Beneficial changes have a way of accumulating, while detrimental ones have a way of being cleared out. This means that while the sudden appearance of beneficial mutations might not be very common, they don't have to be common to become fixed in short order and spread throughout the population with a few generations. Likewise, a frequent appearance of harmful mutations doesn't mean that those harmful mutations will accumulate, because their bearers are less likely to succeed at reproducing over the generations than those with neutral or beneficial mutations. Like I said before, we've been culturing yeast for many thousands of years, and it's pretty much remained unicellular for the whole time. It only took a few dozen days of selective pressure to produce multicellular yeast. That's a profound demonstration of the power of non-random selection to affect rapid, significant changes.